Pneumatic spring.



J. HOFMANN.

PNBUMATIC SPRING.

APPLICATION FILED JULY 18,1912.

Patented Nov. 4, 1913.

U Ta sTATns JOSEF-HOFMANN, OF BAUMAROCHE, SWITZERLAND.

PNEUMATIC SPRING.

Specification of Letters Patent.

Patented Nov. 1913.

Application ined .my 1s, i912. serial N6. 710,252.

To all 'whom it* may concern Be it known that I, JOSEF HOFMANN, asubject ofthe Emperor of Austria-Hungary, residing at Baumaro'che,Switzerland, have invented cert-ain new and useful Improve- 'ments inPneumatic Springs, of which the following is a specification.

This invention relates to` a pneumatic spring of that type, in which apneumatic diaphragm is arranged within a rigid receptacle andcooperating with a plunger. In this type of pneumatic springs the plunvger is to be made of smaller diameter than the cylinder in order to havea sufiicientdis tance between the plunger and thecylinder,A

otherwise the diaphragm would be caused -to form an arc of a smallradius and to break between both members. If the dis` tance between theplunger and the cylinder is made relatively large, the. diaphragm formsan arc of a lar e diameter and is not damaged by the mov ment of theplunger.

But in consequence of the plunger being of Vsmaller diameter Athan thecylinder the area 'ger enters the cylinder.

taken from against the casing is lar er than the area put against theplunger W en the latter enters the casing. By this reasonthe diaphragmbecomes folded when the plun- The distance between the plunger and thecylinder ought to be small so that the difference of the areas of theplunger and the cylinder could be equalized by the elasticity of thediaphragm, but the .diaphragmwould be damaged by constructing thepneumatic spring in this manner.

.According to this invention the distance between the piston and thecylinder is made relatively large and in order to equalize the surfacesof both members the surface of the walls of the plunger is enlarged byany suitable means. By so forming the plunger the diaphragm is putagainst the wall without.

available space between the frame and the Wheels of 'the car, the casing1 isv made .of oblongr cross-section, as will be 'best seen from Figs. 3and 4. The longitudinal walls 1 of the casing are parallel, wliileth'erounded lateral walls 1 are conical. The lower part of the casing 1-isjsecured to a box 2 `provided with a lining 3 which forms a guide fora tube 4. A piston member or plunger 5 being screwed to the upper en dof the tube 4 is'also of oblong cross-section, the

distance between the longitudinal walls of the casing and the pistonbeing greater'tha'n the distance between the lateral walls of saidmembers. The longitudinal Walls 5 ott-he piston are provided-withcorrugations, furrows or wrinkles 6 and projections between them of anysuitable form, while the lateral conical walls 5 ofthe piston have. asmooth surface. These parts of the piston need not to be -provided wit-h`corrugations, becaiise at 'this place by the conica-l shape of bothmembers the diaphragm is caused to form an arc of a large diameterevenif the distance bet-Ween both members is a small one. The plunger isprovided inside with a spherical journal ofa supporting rod 7. The lowersupported by plate 8 secured to the axle 9 of the vehicle.

f The upper end of the casing 1 is provided with a vaultedY cover 13 bymeans of bolts 12. The ledge of a preferably thin pneumatic diaphragm 14is held tight between the flanges of the casing 1 and the cover 13. Thediaphragm partly rests against the inspherical journal of'the rod 7 issuitably ner wall of casing l and partly against the plunger 5.

A completely air-tight chamber A is formed by the above describedarrangement.

This chamber is filled with air and is connected to an air-chamber 15-by a pipe 16.

A pneumatic spring as described above is provided at every wheel of thevehicle. Any suitable number of air chambers may be applied.

The device acts as follows: A pressure eX- erted from below on the axle9 causes the plunger 5 to enter somewhat more into the chamberv A. Ifthere were no corrugations' on the piston, the diameters of the casingbeing larger than those of the plunger, the

area of diaphragm taken from against thev casing 1 could not be putagainst the piston without becoming folded. The excess amount ofdiaphragm is taken up by the corrugations 6 of the piston. By this meansthe diaphragm is prevented from becoming folded or brol{en,'and thediaphragm forms in every position of the pneumatic spring an arc' 14 ofa large radius between the piston and the casing. The describedpneumatic spring is of that type in which the effective area of thediaphragm increases with the increase of the load as the two membersapproach one another. But the invention may as well be applied to anypneumatic spring in which a pneumatic diaphragm is arranged within arigid receptacle and cooperating with a plunger. IfD the cylinder andthe plunger are made of circular crosssection, the plunger is corrugatedall around.

Vhile I have thus described my invention, I wish it to be distinctlyunderstood, that I do not limit myself to the exact details shown anddescribed, as these might be varied widely Without departing from thespirit of my invention.

I claim:

l. In a pneumatic spring, a cylinder member, a piston member and adiaphragm between the members, the area of the crosssection of saidkpiston being limited through an undulated line.

2. In a pneumatic spring a cylinder member, a piston member and adiaphragm between the members andcorrugations provided on the surface ofthe piston member.

3. In a pneumatic spring a cylinder member, a piston member and adiaphragm between the members, the effective area of the diaphragmincreasing with the increase of the load as the two members approach oneanother, and corrugations provided on the surface of the piston member.

4. In a pneumatic spring a cylinder member 'having diameterstransverseto one anotherof different length, a piston member, adiaphragm between the members andv corrugations provided on thelongitudinal walls of said piston member, the longitudinal walls of bothmembers being parallel, While the lateral walls of both members divergefrom one another toward the interior of the cylinder member. Y

In testimony whereof I aix my signature in presence of two Witnesses.

JOSEF `HORMANN.

Witnesses 'IHnonoizn F. DWIGHT, I/VILLIAM S. McCoY.

